what is the difference between .pag file and .ind file ?
I know the page file contains actual data means data-blocks and cells and index file holds the pointer of data block i.e. available in page file.
but is there any other difference ?regarding size?
As per my opinion size of page file is always larger than index file. Is it write? If the size of Index file is larger than page file then what happened?If size of index file is larger than page file then is write?
If I have deleted the page file then it's affect to index file? or If I have deleted some data-block from page file then how is affect to index file?
You are correct about the page file including the actual data of the cube (although there is no data without the index, so in effect they are both the data).
Very typically the page files are bigger than the index. It's simply based on the number of dimensions and whether they are sparse or dense, the number of stored members in the dimensions, the density of the data blocks, the compression scheme used in the data blocks, and the number of index entries in the database.
It's not a requirement that one be larger than the other, it will simply depend on how you use the cube. I would advise you to not really worry about it unless you run into specific performance problems. At that point it is then useful, if for the purposes of optimizing retrieval, calc, or data load time, whether you should make a change to the configuration of the cube.
If you delete the page file it doesn't affect the index file necessarily, but you would lose all of the data in the cube. You would also lose the data if you just deleted all the index files. While the page files have data in them, as I mentioned, it is truly the combination of the page and index files that make up the data in the cube.
Under the right circumstances you can delete data from the database (such as doing a CLEARDATA operation) and you can reduce the size of the page files and/or the index. For example, deleting data such that you are clearing out some combination of sparse members may reduce the size of the index a bit as well as any data blocks associated with those index entries (that is, those particular combinations of sparse dimensions). It may be necessary to restructure and compact the cube in order for the size of the files to decrease. In fact, in some cases you can remove data and the size of the store files could grow.